Synthesis of musical tones



March 31, 1936. R. H. RANGER SYNTHESIS OF MUSICAL TUNES Filed Oct. 22, 1931 5 Shets-Shegt 1 I'llllllL a 9 9 4 a 0 l w e m 0, 2:111 11 w Mk 9 m7 V fan "'6 Ha m-(1 5001 l/ib March 31, 1936.

R. H. RANGER SYNTHESIS OF MUSICAL TONES Filed 05%,. 22, 1931 s Sheets-Sheet 2 March 31, 1936. R. H. RANGER SYNTHESIS OF'MUSICAL TONES Filed Oct. 22, 1931 3 Sheets-Sheet 5 5X INVENTORW "Patented Mar. 31, 1936 PATENT OFFICE SYNTHESIS OF MUSICAL TONES Richard Howland Ranger, Newark, N. .1.

Application October 22, 1931, Serial No. 570,377

42Clalms.

its purity or complexity as a wave of sustained vibrations: in other words, the particular character or quality which identifies a tone is a result of the number, degree, and amplitude of the various harmonic vibrations, commonly called overtones or partials, present in the tone in addition to its fundamental or pitch-setting vibrations. It is these overtones, for instance, which enable a bearer to distinguish at once between a tone produced by a violin and one produced by a comet, even should 'both these tones be of the same pitch and amplitude. The diiferences in timbre between various instruments, skillfully combined and blended by composer and conductor, are responsible for the pleasing variety of tone contained on a good orchestral selection.

Perfectly pure musical tones; that is, those which contain no overtones and may thus be rep- 25 .resented graphically by a sine curve, may be said to have timbre only in a negative sense, much as perfectly pure distilled water may be said to have a negative flavor. Pure tones are occasionally valuable for musical purposes, because of their 3 great clarity, but they have not the richness of complex tones.

It is obvious from the foregoing that an instrument capable of producing tones whose timbre could be varied at the will of the performer should 35 have a much wider application in the'musical art than an instrument producing tones only of a single fixed'timbre. In my co-pending application for Letters Patent, Serial No. 417,466, filed Dec. 30, 1929 now Patent No. 1,901,985, granted I 40' March 21, 1933, I have described a musical system wherein the tones are electrically generated and are essentially sinusoidal or pure in quality.

It is the object of this-invention to describe a means for combining the pure tones of such a 45 system into complex tones of any timbre desired. The most obvious way of attaining this object is of course to analyze the desired complex tones according to the methods of Fourier'into their component simple tones, and then merely to in- 50 troduce these component tones simultaneously and in the proper proportions into the amplifying circuit. In order that this direct method may be used, however, it is necessary to have available sources of tone corresponding to each note of 55 the scale, and to each of the principal harmonics of each of thesenotes. If the wellor equallytempered scale is used as the basis of the system,

as must be the case if occidental music is to be performed, this means that over" 300 separate sources of tone must be provided for a '70 note 5 scale, assuming that each complex tone contains 5 harmonics in addition to its fundamental tone. The octaves of the fundamental tone may be used to provide the second and fourth harmonics, but the third, fifth, and sixth must be separately generated.

Should it be possible, on the other hand, to produce complex tones containing the odd harmonies of the fundamental in any desired proportion, without the necessity of generating these harmonic tones separately, the entire musical system would of course be much less expensive, less complicated, and easier to operate and maintain. Accordingly, it is in this manner that complex musical tones are produced by the present invention.

To illustrate the underlying principles of the invention, and its application to the musical systo the one shown in Fig. 3 of the above-mentioned patent; Fig. 6, showing an altered form of the same amplifier circuit better adapted to be combined with the circuit of the present invention; and Fig, '7, a circuit diagram of the console stop and relay system for controlling the timbre of a complete electrical organ by employing the system of my invention. Figs. 8 and 9 show a side 40 view and a plane view respectively of the tone generating means.

Transformer l of Fig. 1 represents the input transformer of either the first or an intermediate stage of an electrical music system amplifier. Across terminals 2 and 3 of this transformer is fed the fundamental tone of the complex musical note which is to be reproduced by the loudspeaker of the system. From the secondary winding of transformer l the tone is fed into the grids of the thermionic amplifier tubes 5 and 0, connected in the well-known push-pull fashion as shown, and from the plates of these tubes are amplified tone passes to the primary winding of transformer I and thence to the next amp1i- 55 lead from the center tap 8 of the secondary winding 9 of transformer l to the common cathode lead of tubes 5 and E is the secondary of an interstage transformer is, into which is fed the output of amplifier tube H. The input to tube ii is fed in across terminals i2 and i3, passing through transformer id. The grid bias oftubes 5 and 8 is regulated by means of resistor 85.

It'is a well-known fact that in a circuit of the type shown in Fig. i, if the grids of the push-pull amplifier tubes be biased at about normal value and then subjected to a signal voltage greatly in excess of the rated value of the tubes, an appreciable electronic current will flow between the grid and the cathode during a major portion of each cycle of the input wave; that is, during that portion of each cycle when the instantaneous sum. of the grid bias voltage and the applied signal voltage is positive with respect to the cathode of the tubes. This electronic grid current causes an internal impedance drop in the transformer secondary winding and introduces distortion into the amplifying action of the tubes, so causing nu merous harmonics of the input tone to appear in the output tone. Since the circuit is of the pushpull type, the even harmonics will very nearly cancel out: their amplitudes will in any case be negligible compared'to that of the lower odd harmonies. Furthermore, by regulation of the effective grid potential (by varying either the input voltage or the grid bias) any desired one of the odd harmonics may be made to predominate in the output tone.

A more extended explanation of the action of thermionic amplifiers when caused to distort in the manner explained above maybe found on pp. 980-962 of Principles of Radio Communication, by J. H. Morecroft (second edition, John Wiley & Sons, New York), and in the Bell Laboratories Record of April, 1927.

By introducing regulated distortion into the amplifier circuit shown in Fig. l, I have been able to produce complex tones at the output terminals of transformer l containing any desired amount of third harmonic component up to 15% of the total, and any desired amount of fifthharmonic up to 8% of the total, while feeding in a pure fundamental tone across terminals 2 and 3..

Thus'by feeding in also the requisite even harmonic components I am able to produce a great range of full complex tones in the loud speakers of my musical system without the necessity of generating any of the odd components.

This distortion method of tone composition is, however, rather limited in practice, since many complex tones which are musically very desirable require a greater percentage of third, fifth, and sixth harmonics than can be obtained by this means without introducing undesirably large second and fourth harmonic components. Accordingly, I introduce a modulating or heterodyne efiect .into the amplifying circuit by feeding in the second and/or the fourth harmonic of the fundamental tone across terminals 12 and E3 of transformer it. These even harmonics, so fed in, combine with the fundamental tone to produce odd harmonic components representing the sums of and the differences between their frequencies and that of the fundamental, these odd harmonics appearing in the output tone passing through transformer 7, while the heterodvning even harmonics are balanced out between the push-pull tubes 5 and 6.

Assume now that the distorting push=pull amaoeaesc "The curve of Fig. 2 represents the total third harmonic potential available at the secondary winding of transformer l, and is plotted for 'various phase angles between the fundamental tone and the modulating second harmonic. This curve, which I have determined experimentally, shows the third harmonic to be a maximum when the modulating tone lags the fundamental by 45 degrees or cycle of the fundamental frequency. Conversely, the third harmonic approaches a minimum when the phase angle is 45 degrees lead.

It is possible also to vary the third harmonic content of the output wave by varying the intensity of the modulating wave, as shown by the curve of Fig. 3. In determining this curve the phase relation of modulating tone tofundamental was set at 45 degrees 'lag. As shown by Fig. 3, the third harmonic component at first rises as the strength of the modulating tone is increased, until a peak is reached at point A. Further in-' crease of the modulating voltage then causes a decrease in the third harmonic component of the output tone, probably due to a secondary heterodyne efiect in the amplifying circuit, until a minimum is reached at B, whereafter the curve rises again to a second maximum at C.

Operating the circuit of Fig. 1 under the most favorable overload conditions for producing the third harmonic in the output, and introducing the proper value of second harmonic modulation through transformer M to give the condition shown at mam'mum point A of Fig. 3, I am able to vary the third harmonic content of the output tone between limits 5 and 50% of the total by shifting the phase of the modulating tone.

Either distortion or modulation, of course, will of itself be sufilcient to introduce the third harmonic component, but the method here described is capable of producing much larger third harmonies than could ever be produced by distortion alone, and requires only a small fraction of the modulating tone voltage necessary to produce a corresponding efiect by pure heterodyning. In addition to this, regulation of the phase of the modulating tone provides an ideal method of control.

If a fourth harmonic modulating tone is introduced at terminals l2 and I3, it also will heterodyne in the amplifying circuit, producing a fifth harmonic tone aswell as another third harmonic. When both asecond and a fourth harmonic modulation are used, and the two modulating waves are exactly in phase, .the third harmonic heterodyne product of the fourth harmonic modulation is degrees out of phase with that of the resultant of the other third harmonic waves present in the circuit, so that, as shown in Fig. 4, increase of the fourth harmonic modulation will result in an increased fifth harmonic component in the output wave and a proportional decrease in the third harmonic component. All

quantities except the fourth harmonic modula 4. Under these conditional am able to regulate the fifth harmonic content of the output wave at will.

The modulation of the fundamental wave described above need not be limited to the use of even harmonic modulating tones. Odd harmonic or even enharmonic or dissonant tones may be introduced in this manner and caused to tones. A special effect making use of enharmonic modulation will be described below.

Fig. 5 shows a portion of the electrical music system amplifier circuit shown in Fig. 3 of Patent No. 1,901,985, altered to accommodate the system of tone synthesis of the present invention. Transformer 296, bridging the first and second stages of the amplifier, here fulfills the same purpose as transformer I of Fig. 1. The secondary winding of transformer I9 is connected in series with the secondary center-tap lead of transformer 296, and tube II and transformer I4 are connected in exactly as in Fig. 1, tubes 296 and 299 corresponding to tubes 6 and 5 of Fig. 1, and transformer 95I to transformer 1 of Fig. 1. The fundamental tone and the even harmonics of the complex note to be synthesized feed into the amplifier through leads, H5, H6, H1, H9, and 9, adjustable resistors I46, I41, I49, I49, and I59, transformers I49, I, I42, I43, I44, and I45, and tubes 266, 261, 269, 269, 219, and 2", appearing in the secondary circuit of transformer 296 at suflicient voltage to cause distortion in the push-pull amplifier tubes 296 and 299. At the same time modulating second and/or fourth harmonic tones are fed in as explained above through transformer I4, tube II, and transformer I9, thesemodulating tones being appropriately adjusted as to phase and amplitude. Thus the full complex note appears in the secondary cir-' cult of transformer 95I and is then further amplified and reproduced. The grid bias of push-pull tubes 296 and 299 is set by means of adjustable resistor 966, connected to the cathodes of the tubes through lead 956, and to ground at The method of setting the phase of the modulating tones depends of course on the way in which such tones are generated, for instance, if theyare produced by altemators or tone-generators of the type described in the patent, the

phase may be shifted by an arcuate adjustment ings I, 492, 49 9, 494,. 495, and 496 of a special input transformer 4I9. Each of the primary windings of transformer 4I9 is matched to the tone input line, while its secondary winding 4 matches the grids of push-pull tubes 299 and 299. Since the secondary winding 4| I feeds directly to the grids of a push-pull amplifier stage, the

W modulation input circuit'(transformer I9, tube II, and transformer I4) may be connected in series with the secondary mid-tap lead 4I2 as shown. From the push-pull stage on, the amphfier circuit is exactly the same as that of Fig. 5. Another stage of amplification may be added if necessary, but I have not found it so.

In addition to the reduction in the relative amplitude of the modulating fourth and second harmonic tones, and the consequent greater range of modulation made possible by the circuit of Fig. 6, the latter has the further advantages of materially reducing the number of vacuum tubes needed for the system, thus making it cheaper and easier to maintain, and of precluding the possibility of cross-modulation between the fundamental tone and the various even harmonics fed in through leads H6, H6, III, III, and H9. In the circuit of Fig. 5 all these tones, passing through their individual input tubes, are connected in parallel to the primary winding of transformer 296, and may thus modulate each other. In the circuit of Fig. 6 the tones are separately induced in secondary winding H I, and are consequently less likely to modulate each other.

Were each of the component tones of a desired complex note available at the amplifier input, the' amplifier circuit of Fig. 3 of Patent No. 1,901,985 would undoubtedly be the most desirable, due to its great flexibility. Using the tone synthesizing method of the present invention, however, the circuit of Fig. 6 of this application 'is' far superior to that of Fig. 5.

Fig. 7 shows a complete system of timbre control for an electrical organ'such as the one described in the above noted patent. With the control system here shown, the performer has at his command a virtually unlimited range of tone quality. The switches contained within the dotted square to the upper right of Fig. 7 represent stops, tilting tablets, or other convenient means of control located at the organ console, and wires II9, III, H2, H9, H4 and H5 are each assumed to carry the fundamental or ground tone of one of six different notes resulting from the performers depression of six keys of the organ manual.

It will be recalled that in an electric organ of the type disclosed in the patent each note played selects an idle amplifier and reproducer, which is then reserved for the exclusive use of that note as long as the corresponding key is depressed. Thus wires II9, III, II2, I|3, H4, and H5 would each ordinarily pass to one of say six amplifier and reproducer assemblies. Instead of this, each wire passes to one of the contacts on each of the four relays R11, R12, R13, R14, controlled respectively by stop switchesfi, 1:. 1:, and I4. For example, wire H5 is connected to contact 49 of relay R11, contact 46 of relay R12, contact 52 of relay R13, and contact 58 of relay R14; wire H4 is connected to contact 4| of relay R11, contact 41 of relay Rh, contact 59 of relay R13, and contact 59 of relay R14, and so on. From the relay contacts, the tones pass through the amplitude regulating resistors associated therewith, and then through cable C2 to the contacts of relay RMi. When relay RM1, is in its openposition, the six tones pass through contacts 65, 61, 69, II, 19 and I6 to cable C1, and thence through a selector system to their six separate amplifier and reproducer units. when relay RM1 is closed, however,

the six tones'pass through contacts, 66, 99, 19, 12, and I4 to wires I26, I29, I2I, I24, I22,

and I29, and each of these wires feeds its tone in modulator'fashion into one of the six ampliflers available. In other words, assumingthe type amplifier shownin Fig. 6 to be used, a fundamental tone selecting this amplifer would, with relay RM; open, pass through lead III,

, contacts of relay R115, to the amplifiers. nections are indicated only for the control relays modulating tone.

'resistor' H36, and primary windings 589, and ltf. With relay RMi closed it would pass through transformer l l, tube ii, and transformer 9i Relays R11, R12, R13, and R14 control the percentage of fundamental tone present in the final reproduced note by means of the amplitude regulating resistors already mentioned. Relay R11, for instance, has its associated resistors I5, 16, ll, 4%, l9, and 28 so adjusted that, with a given amplitude of tone coming in on leads 5 Hi, i i l, 9 H2, H3, Md, and lit, it will pass tones as strong as those passed by either R12, or R13, and as strong as those passed by R14. Tnus by closing switches 11, I2, 13, and 14, in various combinations, ten different amplitude steps of the fundamental tones are available between zero and an arbitrary maximum determined by the strength of the input tones to the timbre control system; Closing switches 11, 12, and 14, simultaneously, for instance, would permit fundamental tones 80% of the maximum value to be passed on to the contacts of relay RM1, sinoerelays R11, R12, and R14, would close, positive potential reaching them through leads lflii, ill! and 33.

A bank of relays similar to R11, R12, and R13,

and R14 is provided for the control of each order 'of partial of the notes to be reproduced by the organ. Relays R111, R112, R113, and R114, operated by positive potential supplied from switches 111, 112,113, and 114, through a cable similar to C1, regulate the amplitude of the second partials (or first harmonics) of the fundamental or first partial tonescontrolled by relays R11, R12, R13, and R14, in an exactly similar fashion to the latter relays, passing the second partial tones on through cable C3 to relay RM2. In the same way relays RlVi, RIVz, RIV3, and R1174, control the amplitude of the fourth partial tones and relays RVIH1, avmz, RV1113, and RVIII, the amplitude of the eighth partial tones of any notes reproduced by the organ, relays Rlvla, and Rivh, serving to mix these partial tones in the amplifiers either directly or in modulating fashion. Relays R311, RXaRfi, and RXi, may be used to pass at any desired amplitude any additional tone or tones, whether harmonic or enharmonic, necessary to produce specialeifects in timbre. These tones then pass through cable Cs, and the Confor the fundamental tones in Fig. 7, due to space limitations.

Should it be desired to feed the first partial tones of a complex note to theamplifier both directly and as a modulating tone, this may be effected y the simultaneous closure of switch 200 and s itch M1. The tone will then feed normally to the amplifier through cable C11, which is appropriately connected to a selector system, at the same time that relay RMI is feeding it as a Switches similar to 289 are provided for each relay bank, and like the single-pole stop switches are operable from the console.

One of the most striking synthetic timbre effects obtainable with an electrical organ, and one which illustrates Well the use of the timbre control system of Fig. 7, is the bell. When a hell or any other percussion type musical instrument is struck sharply by a hammer or clapper, the note it produces at first is extremely impure. The force of the blow tends to change the characteristics of the bell so that it vibrates at some frequency slightly higher than its normal rate. Numerous minor vibrations are also set up, small aosaase areas of the bell surface acting as individual sounding bodies. These parasitic vibrations are highly damped, however, and soon subside,leav-= ing only the normal tone of the bell audible, together with a few weal: harmonic tones.

I. achieve the bell efiect by feeding into relays RXi, RX2, RF, and R214 two enharmonic and one harmonic component for the final complex tone; namely, the tonesa musical second and a musical third above, and the tone two octaves below the fundamental tone feeding into relays R11, R12, R13, and R14. 1 thus have available in physical terms, a complex tone wave made up of vibrations at three frequencies;

and 0.25 times the frequency of the fundamental tone respectively. 1 now close switches 11, 12, I4, 113, 1V1, X1, X2, X3, X4, M2, and Ms, thus operating the corresponding relays R11, R12, R14, R113, RIVi, RX1, R RXs, R114, RM2, and Rlvls. Through relays R11, R12, and R14, fundamental tone is supplied normally to the amplifiers at 80% of its maximum value, to mix with 10% of the maximum fourth partial supplied through relay RIV1. Relay RHs, supplies 20% of the. maximum second partial tone, and this, together with the full value enharmonic tones coming through relays RXr, RXz, R113 and R114, is fed as a modulating wave to the amplifiers, by virtue of the closure of relays Rlvlz and RMs. The resultant note thus contains a strong fundamental tone, weak third and fifth partial components produced by the modulating second partial, a-

v second key-board or manual. By some appropriate means 1 then cause the plate supply of the amplifier passing the full tone including the enharmonic components to die away logarith mically, causing the full complex tone to die away likewise, leaving only the comparatively pure note controlled by the second manual. In

this way the bell-tone is closely imitated. A con-' veniently applicable means of achieving such a decaying plate supply for an amplifier is fully disclosed by me in Letters Patent No. 1,901,968, granted March 21, 1933. 1 have, in fact, applied the general principles disclosed in said patent to the principles of the present invention to make possible effects such as the bell. In combination with the synthesizing method of the present invention in the manner described above many pleasing musical effects may be attained. The component proportions of the partial tones in the bell effect described above need not be strictly adhered to, of coursean infinite variety of bell-qualities may be produced by changing the proportions slightly, just as slight changes in the manner of casting an actual bell will change its tone quality. 7

Many entirely new musical effects may be achieved by varying the details of design of my plied through an amplifier whose plate supply is obtained from a charging condenser, thus causing the enharmonic tones to increase logarithmically in amplitude after the manual key is depressed. A most unusual effect is obtainable by subjecting tube II to the action of a tremolo device such as the one described in Patent No. 1,901,985. In this way a tremolo is superimposed upon the'modulating harmonic tones, and the flnal complex tone has what may be called a timbre-tremolo, its quality changing regularly at the tremolo rate.

Having now described my invention, and feeling myself entitled not only to the specific -em-. bodiments thereof discussed above, but also to such variations in design which might be judged as falling'fairly within the spirit and scope' of my invention, what I claim is the following:

1. The method of producing synthetic musical notes which comprises supplying to a modulating electrical circuit in modulating relation oscillations comprising as a component oscillations of the frequency of the fundamental of the note to be produced and modulating oscillations comprising as a component oscillations of a different audio frequency.

2. In an electrical music system, a plurality of tone generators for generating frequencies corresponding respectively to consecutive notes on a musical scale throughout a plurality of octaves, a plurality of amplifying systems foramplifying the tones generated in accordance with a predetermined note selection, a sound-reproducer coordinated with each of the said amplifying systems, and circuits for connecting each of said amplifying systems with those tone generators supplying the fundamental tone and the even numbered partials of a note of a musical scale to be produced, including a divided input circuit having a common portion and means for connecting one tone generator to the common porhaving a tion of said divided input circuit.

3. In an electrical music system, a plurality of tone generators for generating frequencies corresponding respectively to consecutive notes on a musical scale throughout a plurality of octaves, a plurality of amplifying systems for amplifying the tones generated in accordance with a predetermined note selection, a sound-reproducer coordinated with each of the said amplifying systems, and circuits for connecting each of said amplifying systems with those tone generators supplying the fundamental tone and the even numbered partials of a note of the musical scale to be prsduced, including a divided input circuit ,common portion and a circuit for additionally supplying one of said tones to the common portion ofthe divided input circuit, provision being made for causing said amplifying systems to draw grid current.

4. In an electrical music system, a plurality of tone generators for generating frequencies corditionally connecting one of said tone generators 1 .to the common portion of the divided input circuit, said divided circuit having the common portion connected to each of two control electrodes of parallel electrical discharge devices forming a part of said circuit, provision being made for causing the amplifying systems to draw grid current from said divided circuit.

5. In an electrical music system, a plurality of tone generators for generating frequencies corresponding respectively to consecutive notes on a musical scale throughout a plurality of octaves, a. plurality of amplifying systems for amplifying the tones generated in accordance with a predetermined note selection, a sound reproducer coordinated with each of the said amplifying systems, circuits for connecting each of said amplifying systems with those tone generators supplying the fundamental tone and the even numbered partials of a note of a musical scale to be produced including a multi-primary transformer and a divided input circuit having a common portion and circuits for additionally connecting one of said tone generators to the common portion of the divided input circuit, said common portion having an individual portion connected to each of the control electrodes of apair of electrical discharge devices forming a part of the input circuit of said amplifying systems, provision being made for causing said amplifying system to draw d current.

6. In an electrical music system as described in claim 3, means for separately controlling the intensity of each of the fundamental and partial frequencies supplied to said amplifiers in accordance with the tone quality desired.

7. In an electrical music system as described in claim 3, means for varying the relative phase of the tones supplied through the common branch of the divided input circuit in accordance with the tone quality desired.

8. The method of simulating by electrically generated tones the timbre of a percussion type musical instrument which comprises the admixture with a fundamental tone and its related partial tones of a plurality of enharmonic tones of frequencies higher than that of the said fundamental tone, the simultaneous reproduction of the resulting composite tone with a second composite tone containing only the said fundamental and the said related partial tones, and the maintenance of the said second composite tone at its original amplitude while the amplitude of the first composite tone is reduced logarithmically until it is no longer audible.

9. In an electrical music system as described in claim 3, means for varying the amplitude of 'the tones supplied through the common branch of the divided input circuit between predetermined limits at a predetermined rate.

10. The method of producing synthetic timbre effects in an electrical music system which com- .prises the admixture of two compound tones, the

first compound tone consisting of a fundamental audio frequency tone and various partials thereof, and the second compound tone consisting of the said fundamental tone, the said partial tones, and a plurality of enharmonic tones of frequencies higher than that of the'said fundamental tone, the simultaneous reproduction of the said first compound tone with the said second compound tone, and the increase or decrease in amplitude of either or both of said two compound tones at separately predetermined rates during said reproduction.

11. The method of producing synthetic musical notes defined in claim 1, wherein the modulating oscillations are of a frequency corresponding to a partial of a note to he produced.

12. The method of producing synthetic musical notes defined in claim 1, wherein the modulating oscillations are compounded of oscillations of a plurality of frequencies each corresponding to a partial of thenoteto he produced.

13. The method of producing synthetic musical notes defined in claim 1, wherein the modulating oscillations are composite oscillations compr sing as components oscillations of frequencies corresponding to the second and fourth partials of the note to he produced. r 1

14. The method of producing synthetic musical notes which comprises supplying to the individual portions of a frequency translating circuit, in-

. eluding a pair of electrical discharge devices each.

' having an anode, a cathode and a controlelecnotes which comprises supplying to the individual portions oi a frequency translating circuit, including a pair of electrical discharge devices each having an anode, a cathode and a control electrode, a divided input circuit therefor having an individual portion connected to each of said control electrodes respectively and a coon portion connected to said cathodes and a divided output circuit having an individual portion connected to each of said anodes and a common portion connected to said cathodes, oscillations of the frequency of the fundamental tone of the note to be produced, regulating the effective grid potential to introduce distortion in the current produced in the output circuit thereby producing harmonic components and supplying to the common portion of the input circuit oscillations of a frequency corresponding to that or a partial of the note to be produced.

16. The method of producing synthetic musical notes'which comprises supplying to the individual portions of a. frequency translating circuit, in-

cluding a. pair of electric discharge devices each having an anode,a cathode and a. control electrode, a divided input circuit therefor having an individual portion connected to each of said control electrodes respectively and a common portion connected to said cathodes, a divided output circuit having an individual portion connected to each of said anodes and a, common portion con- 'nected to said cathodes, oscillations of the frequency of the fundamental tone of the note to be produced and supplying to the common portion of said input circuit oscillations of audio frequency. g

17. The method of produclngsynthetlc musical notes as defined in claim 16, wherein the oscillations supplied to the common portion of the input circuit are of a. frequency corresponding to that of a partial ofthe noteto be produced.

18. The method of-prcducing synthetic musical notes as defined in claim16, wherein the dscil-" lotions supplied to the common portion of the accused input circuit are compounded of oscillations of a plurality of frequencies each corresponding to the frequency of a partial of the note to he produced.

19. The method oi producing synthetic musical notes as defined in claim it, wherein the oscillations supplied to the common portion of the input circuit are composite oscillations comprising as components oscillations of frequencies corresponding to those of the second and fourth partials of the note to he produced.

20. The method of producing synthetic musical notes which comprises supplying to the individual portions of a frequency translating circuit, including a pair of electric discharge devices each having an anode, a cathode and a control electrode, a divided input circuit therefor having an individual portion connected to each of said control electrodes respectively and a common portion connected to said cathodes and a divided output circuit having an individual portion connected to each of said anodes and a common portion connected to said cathodes, oscillations comprising as components oscillations of the frequency of the fundamental and of a partial of the note to be produced, supplying to the common portion of said input circuit oscillations of the frequency of an even partial and adjusting the phase of the last mentioned oscillations to produce the desired intensity of the partials in the output.

21. The method of producing synthetic complex notes which comprises supplying to a modulating electrical circuit oscillations having a frequency corresponding to the fundamental of a note to be produceddistortingsaid oscillations to introduce a harmonic component and supplying also to said circuit modulating oscillations having a frequency corresponding to a partial of the note.

22. The method of producing synthetic complex notes which comprises supplying to a modulating electrical circuit oscillations having a frequency corresponding to the fundamental of a note to be produced distorting said oscillations to introduce an odd partial component and supplying also to said circuit modulating oscillations having a frequency corresponding to an even partial of the note, and thereby to produce by modulation an odd partial of the same frequency as the odd partial introduced by distortion and shifting the relative phase of the even partial to vary the resultant total intensity of the above-mentioned odd partial.

24. An electrical musical system comprising a modulating electrical circuit, means for supply ing to one portion or sold circuit current having a note to be produced and means for supplying to another portion of the circuit in modulating relation current having a component of audio frequency. 1

25. An electrical musical system comprising a modulating electrical circuit, means for supplying to one portion of said circuit current having a component of the frequency oithe fundamental oi a note to he produced and a component of the 65 component of the frequency of a ia-l oi a modulating relation current the principal component of which is of the frequency of a partial of the note and means for regulating the relative phase of the modulating current.

26. An electrical musical system comprising a modulating electrical circuit, means for supplying to said circuit in modulating relation current of a frequency corresponding to that of the fundamental of a note to be produced and current of a frequency corresponding to that of a partial of said tone.

27. An electrical musical system comprising a modulating electrical circuit, means for supplying to said circuit in modulating relation current of a frequency corresponding to that of the fundamental of a note to be produced and current of a frequency corresponding to that of the second partial of the note and means for distorting the first mentioned current to cause a component corresponding to an odd partial of the note to be introduced.

28. An electrical musical system comprising a modulating electrical circuit, means for supplying to said circuit in modulating relation current of a frequency corresponding to that of the fundamental of a note to be produced and current of a frequency corresponding to that of the second partial of the note, means for distorting the first mentioned current to cause a component corresponding to an odd partial of the note to be introduced and means for adjusting the phase of one current relative to the other.

29. An electrical musical system comprising a frequency translating circuit including a pair of electric discharge devices each having an anode,

a cathode and a control electrode, a divided input.

circuit therefor having an individual portion connected to each of said control electrodes respectively and a common portion connected to said cathodes, means for supplying an oscillating electrical current of audio frequency to said individual portions, means for supplying an oscillating electrical current of audio frequency to said common portion, and a divided output circuit having an individual portion connected to each of said anodes and a common portion connected to said cathodes.

30. An electrical musical system comprising a push pull modulating electrical circuitincluding a divided input circuit with a principal transformer connected to the side portions and a second transformer connected to the centre portion, means for supplying audio frequency electrical current to the principal transformer and means for supplying audio frequency electrical current to the second transformer.

31. An electrical musical system comprising a push pull modulating electrical circuit including a divided input circuit with a principal transformer connected to the side portions and a second transformer connected to the centre portion, means for supplying audio frequency electrical current to the principal transformer, means for supplying audio frequency electrical current circuit therefor having an individual portion connected to each of said control electrodes respectively and a common portion connected to said cathodes, means for supplying audio frequency current to said individual portions, means for regulating the effective potential of the control electrodes to modify the character of the current, and means for supplying audio frequency current to the common portion of the circuit.

33. An electrical musical system comprising a frequency translating circuit including a pair of electric discharge devices each having an anode,

a cathode and a control electrode, a divided input cathodes, a divided output circuit having an individual portion connected to each of said anodes and a common portion connected to said cathodes, means for supplying, current of a frequency of the fundamental of a note to be produced to said individual portions of the input circuit, means for regulating the effective potential of the control electrodes to modify the wave character of the current in the output circuit to produce an additional harmonic wave therein, and means for supplying a current of a frequency corresponding to that of a partial of the note to-be produced to the common portion of said input circuit.

- 34. An electrical musical system comprising a frequency translating circuit including a pairof electric discharge devices each having an anode, a cathode and a control electrode, a divided input circuit therefor having an individual portion connected to each of said control electrodes respectively and a common portion connected to said cathodes, a divided output circuit having an individual portion connected to each of said anodes and a common portion connected to said cathodes, means for supplying current of a frequency of the fundamental of a note to be produced to said individual portions of the input circuit, means for regulating the effective potential of the control electrodes to modify the character of the current in the output circuit to produce therein additional oscillations corresponding to the frequency of an odd partial of the note, means for supplying a current of a frequency corresponding to that of an even partial of the note to the common portion of said input circuit and means for regulating the relative phase of said last mentioned current.

35. An electrical musical system comprising a frequency translating circuit including a pair of electric discharge devices each having an anode, a cathode and a control electrode, a divided input circuit therefor having an individual portion connected to each of said control electrodes respectively and a common portion connected to said cathodes, a divided output circuit having an into the individual portions of the input circuit,

means for supplying a second current of audio frequency to the common portion of the input circuit said latter means including an amplifier with a plate circuit having therein a relatively large condenser arranged to cause relatively high plate circuit current when the note is initiated followed by fading.

36. The method of producing synthetic complex notes'which comprises supplying to an electrical circuit current having a component of a frequency corresponding to the fundamental of a note to be produced, supplying simultaneously to said circuit current having a component of a frequency of an enharrnonic of the note and gradually reducing the amplitude of the enharmonic waves while maintaining the amplitude of the first mentioned waves. 7

37. The method of producing synthetic complex notes which comprises Supp -W 8 to a modulating electrical circuit composite oscillations having components of audio frequencies corresponding to the fundamental and selected partials, supplying also to said circuit modulating oscillations having components of frequencies corresponding to selected enharmonics and maintaining the amplitude of the first mentioned oscillations while gradually reducing the amplitude of the modulating oscillations.

35. The method of producing synthetic musical notes which comprises supplying to an electrical circuit in modulating relation two oscillatory electrical currents of audio frequency.

39. The method oi producing synthetic musical notes which comprises supplying to an electrical circuit oscillations of the frequency of a partial of v aosaese 40. Apparatus for producing a musical note comprising means for producing oscillations of audio frequency, a second means for producing oscillations of audio frequency, means for causing the second oscillations to modulate the intensity of the first oscillations and means for shifting the phase of the modulation.

e1. The'method of producing .a complex musical note which comprises passing oscillations of the frequency of one partial of the note through an amplifiertube andvarying the momentarily efiective output of the tube at a rate corresponding to the frequencyof another partial of the note.

42. In the operation of an electrical musical trical circuit having a divided input circuit with a principal transformer connected to the side portions and a second transformer connected to the center portion, the method of producing synthetic complex notes which comprises supplying to the principal transformer audio frequency electrical current and supplying to the second transformer audio frequency electrical current.

a. n. RANGER. 

